Multi-speed transmission

ABSTRACT

A transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may include clutches and brakes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/057,945 filed on Mar. 28, 2008 which claims the benefit of U.S.Provisional Application No. 60/912,771 filed on Apr. 19, 2007. Thedisclosure of the above application is incorporated herein by reference.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices and more particularly to a transmission havingeight or more speeds, four planetary gear sets and a plurality of torquetransmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of frictionclutches, planetary gear arrangements and fixed interconnections toachieve a plurality of gear ratios. The number and physical arrangementof the planetary gear sets, generally, are dictated by packaging, costand desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member,four planetary gear sets, a plurality of coupling members and aplurality of torque transmitting devices. Each of the planetary gearsets includes first, second and third members. The torque transmittingdevices are for example clutches and brakes.

An embodiment of the transmission includes an input member, an outputmember, and first, second, third and fourth planetary gear sets eachhaving a sun gear, a carrier member, and a ring gear, wherein the inputmember is continuously interconnected with the sun gear of the thirdplanetary gear set and the carrier member of the fourth planetary gearset and the output member is continuously interconnected with thecarrier member of the third planetary gear set. A first interconnectingmember continuously interconnects the ring gear of the first planetarygear set with the carrier member of the second planetary gear set andthe ring gear of the third planetary gear set. A second interconnectingmember continuously interconnects the sun gear of the first planetarygear set with the sun gear of the second planetary gear set and the ringgear of the fourth planetary gear set. A first torque transmittingdevice is selectively engageable to interconnect at least one of thecarrier member of the fourth planetary gear set, the sun gear of thethird planetary gear set, and the input member with the carrier memberof the first planetary gear set. A second torque transmitting device isselectively engageable to interconnect at least one of the ring gear ofthe fourth planetary gear set, the sun gear of the first planetary gearset, and the sun gear of the second planetary gear set with at least oneof the carrier member of the third planetary gear set and the outputmember. A third torque transmitting device is selectively engageable tointerconnect the sun gear of the fourth planetary gear set with astationary member. A fourth torque transmitting device is selectivelyengageable to interconnect the carrier member of the first planetarygear with the stationary member. A fifth torque transmitting device isselectively engageable to interconnect the ring gear of the secondplanetary gear set with the stationary member. The torque transmittingdevices are selectively engageable in combinations of at least two toestablish at least eight forward speed ratios and at least one reversespeed ratio between the input member and the output member.

Another embodiment of the transmission of the present invention includesan input member, an output member, and first, second, third and fourthplanetary gear sets each having a sun gear, a carrier member, and a ringgear, wherein the input member is continuously interconnected with thesun gear of the first planetary gear set and the output member iscontinuously interconnected with the carrier member of the thirdplanetary gear set and the ring gear of the fourth planetary gear set. Afirst interconnecting member continuously interconnects the carriermember of the first planetary gear set with the ring gear of the secondplanetary gear set and the ring gear of the third planetary gear set. Asecond interconnecting member continuously interconnects the ring gearof the first planetary gear set with the sun gear of the secondplanetary gear set and the carrier member of the fourth planetary gearset. A first torque transmitting device is selectively engageable tointerconnect the carrier member of the second planetary gear set with atleast one of the sun gear of the first planetary gear set and the inputmember. A second torque transmitting device is selectively engageable tointerconnect at least one of the sun gear of the second planetary gearset, the ring gear of the first planetary gear set, and the carriermember of the fourth planetary gear set with the sun gear of the thirdplanetary gear set. A third torque transmitting device is selectivelyengageable to interconnect the carrier member of the second planetarygear set with a stationary member. A fourth torque transmitting deviceis selectively engageable to interconnect the sun gear of the thirdplanetary gear set with the stationary member. A fifth torquetransmitting device is selectively engageable to interconnect the sungear of the fourth planetary gear set with the stationary member. Thetorque transmitting devices are selectively engageable in combinationsof at least two to establish at least eight forward speed ratios and atleast one reverse speed ratio between the input member and the outputmember.

Further objects, aspects and advantages of the present invention willbecome apparent by reference to the following description and appendeddrawings wherein like reference numbers refer to the same component,element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of an eight speedtransmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of an eight speedtransmission according to the present invention;

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting clutches and brakes in each of the availableforward and reverse speeds or gear ratios of the transmissionillustrated in FIGS. 1 and 2;

FIG. 4 is a lever diagram of another embodiment of an eight speedtransmission according to the present invention;

FIG. 5 is a diagrammatic view of another embodiment of an eight speedtransmission according to the present invention; and

FIG. 6 is a truth table presenting the state of engagement of thevarious torque transmitting clutches and brakes in each of the availableforward and reverse speeds or gear ratios of the transmissionillustrated in FIGS. 4 and 5.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that the embodiments of thetransmission of the present invention have an arrangement of permanentmechanical connections between the elements of the four planetary gearsets in common. These mechanical connections generically link or relatethe transmission embodiments. More specifically, a first component orelement of a first planetary gear set is permanently coupled to a firstcomponent or element of a second planetary gear set and to a firstcomponent or element of the fourth planetary gear set. A secondcomponent or element of the first planetary gear set is permanentlycoupled to a second component or element of a second planetary gear setand to a second component or element of the third planetary gear set. Athird component or element of the third planetary gear set ispermanently coupled to a third component or element of the fourthplanetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10is illustrated in a lever diagram format. A lever diagram is a schematicrepresentation of the components of a mechanical device such as anautomatic transmission. Each individual lever represents a planetarygear set wherein the three basic mechanical components of the planetarygear are each represented by a node. Therefore, a single lever containsthree nodes: one for the sun gear, one for the planet gear carrier, andone for the ring gear. The relative length between the nodes of eachlever can be used to represent the ring-to-sun ratio of each respectivegear set. These lever ratios, in turn, are used to vary the gear ratiosof the transmission in order to achieve an appropriate ratios and ratioprogression. Mechanical couplings or interconnections between the nodesof the various planetary gear sets are illustrated by thin, horizontallines and torque transmitting devices such as clutches and brakes arepresented as interleaved fingers. If the device is a brake, one set ofthe fingers is grounded. Further explanation of the format, purpose anduse of lever diagrams can be found in SAE Paper 810102, “The LeverAnalogy: A New Tool in Transmission Analysis” by Benford and Leisingwhich is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C and an output shaft or member 22.

The first node 14A of the first planetary gear set 14 is coupled to thesecond node 16B of the second planetary gear set 16 as well as to thefirst node 18A of the third planetary gear set 18. The third node 14C ofthe first planetary gear set 14 is coupled to the third node 16C of thesecond planetary gear set 16 and to the first node 20A of the fourthplanetary gear set 20. The third node 18C of the third planetary gearset 18 is coupled to the second node 20B of the fourth planetary gearset 20. The second node 18B of the third planetary gear set 18 iscoupled to the output shaft or member 22. The second node 20B of thefourth planetary gear set 20 is coupled to the input shaft or member 12.

A first clutch 26 selectively connects the input shaft or member 12 tothe second node 14B of the first planetary gear set 14. A second clutch28 selectively connects the third node 16C of the second planetary gearset 16 to the second node 18B of the third planetary gear set 18 and tothe output shaft or member 22. A first brake 30 selectively connects thethird node 20C of the fourth planetary gear set 20 to the ground,stationary member, or transmission housing 50. A second brake 32selectively connects the second node 14B of the first planetary gear set14 to the ground, stationary member, or transmission housing 50. A thirdbrake 34 selectively connects the first node 16A of the second planetarygear set 16 to the ground, stationary member, or transmission housing50.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches, brakes and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, planetary gear set 14 is a planetary gear set that includesa sun gear member 14C, a planet gear carrier member 14B and a ring gearmember 14A. Sun gear member 14C is connected for common rotation with afirst interconnecting shaft or member 42 and a second interconnectingshaft or member 44. Ring gear member 14A is connected to a thirdinterconnecting shaft or member 46. The planet gear carrier member 14Brotatably supports a set of planet gears 14D (only one shown) and isconnected for common rotation with a fourth interconnecting shaft ormember 48. Planet gears 14D are configured to each intermesh with bothsun gear member 14C and ring gear member 14A.

The input shaft or member 12 is continuously connected to an engine (notshown) and to a turbine of a torque converter (not shown). The outputshaft or member 22 is continuously connected with the final drive unitor transfer case (not shown).

Planetary gear set 16 is a planetary gear set that includes a sun gearmember 16C, a planet carrier member 16B that rotatably supports a set ofplanet gears 16D and a ring gear member 16A. Sun gear member 16C isconnected for common rotation with second interconnecting shaft ormember 44 and a fifth interconnecting shaft or member 52. Planet carriermember 16B is connected for common rotation with third interconnectingshaft or member 46 and a sixth interconnecting shaft or member 54. Ringgear member 16A is connected for common rotation with a seventhinterconnecting shaft or member 56. Planet gears 16D are configured toeach intermesh with both sun gear member 16C and ring gear member 16A.

Planetary gear set 18 is a planetary gear set that includes a sun gearmember 18C, a ring gear member 18A and a planet carrier member 18B thatrotatably supports a set of planet gears 18D. Sun gear member 18C isconnected for common rotation with input shaft or member 12. Ring gearmember 18A is connected for common rotation with sixth interconnectingshaft or member 54. Planet carrier member 18B is connected for commonrotation with output shaft or member 22 and a eighth interconnectingshaft or member 58. Planet gears 18D are configured to each intermeshwith both sun gear member 18C and ring gear member 18A.

Planetary gear set 20 is a planetary gear set that includes a sun gearmember 20C, a ring gear member 20A and a planet carrier member 20B thatrotatably supports a set of planet gears 20D. Sun gear member 20C isconnected for common rotation with first interconnecting shaft or member60. Ring gear member 20A is connected for common rotation with firstinterconnecting shaft or member 42. Planet carrier member 20B isconnected for common rotation with input shaft or member 12 and a ninthinterconnecting shaft or member 62. Planet gears 20D are configured tointermesh with both sun gear member 20C and ring gear member 20A.

The torque-transmitting devices or clutches 26, 28 and brakes 30, 32 and34 allow for selective interconnection of the shafts or interconnectingmembers, members of the planetary gear sets and the housing. Forexample, first clutch 26 is selectively engageable to connect fourthinterconnecting shaft or member 48 to ninth interconnecting shaft ormember 62. Second clutch 28 is selectively engageable to connect fifthinterconnecting shaft or member 52 to eighth interconnecting shaft ormember 58. First brake 30 is selectively engageable to connect firstinterconnecting shaft or member 60 to ground, stationary member, ortransmission housing 50 to restrict rotation of shaft or member 60relative to housing 50. Second brake 32 is selectively engageable toconnect fourth interconnecting shaft or member 48 to ground, stationarymember, or transmission housing 50 to restrict rotation of shaft ormember 48 relative to housing 50. Third brake 34 is selectivelyengageable to connect seventh interconnecting shaft or member 56 toground, stationary member, or transmission housing 50 to restrictrotation of shaft or member 56 relative to housing 50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of theeight speed transmission 10 will be described. It will be appreciatedthat transmission 10 is capable of transmitting torque from the inputshaft or member 12 to the output shaft or member 22 in at least eightforward speed or torque ratios and at least one reverse speed or torqueratio. Each forward and reverse speed or torque ratio is attained byengagement of one or more of the torque-transmitting devices (i.e. firstclutch 26, second clutch 28, first brake 30, second brake 32 and thirdbrake 34), as will be explained below. FIG. 3 is a truth tablepresenting the various combinations of torque-transmitting devices thatare activated or engaged to achieve the various gear states. Actualnumerical gear ratios of the various gear states are also presentedalthough it should be appreciated that these numerical values areexemplary only and that they may be adjusted over significant ranges toaccommodate various applications and operational criteria of thetransmission 10. An example of the gear ratios that may be obtainedusing the embodiments of the present invention are also shown in FIG. 3.Of course, other gear ratios are achievable depending on the geardiameter, gear teeth count and gear configuration selected.

To establish reverse gear, first brake 30 and second brake 32 areengaged or activated. First brake 30 connects first interconnectingshaft or member 60 to ground, stationary member, or transmission housing50 to restrict rotation of shaft or member 60 relative to housing 50.Second brake 32 connects fourth interconnecting shaft or member 48 toground, stationary member, or transmission housing 50 to restrictrotation of shaft or member 48 relative to housing 50. Likewise, theeight forward ratios are achieved through different combinations ofclutch and brake engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 10 assumes, first of all,that all the clutches and the brake not specifically referenced in agiven gear state are inactive or disengaged and, second of all, thatduring gear shifts, i.e., changes of gear state, between at leastadjacent gear states, a clutch or brake engaged or activated in bothgear states will remain engaged or activated.

Referring now to FIG. 4, another embodiment of a transmission isillustrated and referenced by reference numeral 100. Transmission 100includes an input shaft or member 112, a first planetary gear set 114having three nodes: a first node 114A, a second node 114B and a thirdnode 114C, a second planetary gear set 116 having three nodes: a firstnode 116A, a second node 116B and a third node 116C, a third planetarygear set 118 having three nodes: a first node 118A, a second node 118Band a third node 118C, a fourth planetary gear set 120 having threenodes: a first node 120A, a second node 120B and a third node 120C andan output shaft or member 122.

The first node 114A of the first planetary gear set 114 is coupled tofirst node 116A of the second planetary gear set 116. The second node114B of the first planetary gear set 114 is coupled to the third node116C of the second planetary gear set 116. The third node 114C of thefirst planetary gear set 114 is coupled to the input shaft or member112. The first node 118A of the third planetary gear set 118 is coupledto first node 120A of the fourth planetary gear set 120. The second node118B of the third planetary gear set 118 is coupled to the second node114B of the first planetary gear set 114. The first node 120A of thefourth planetary gear set 120 is coupled to the output shaft or member122. The second node 1208 of the fourth planetary gear set 120 iscoupled to the first node 114A of the first planetary gear set 114.

A first clutch 126 selectively connects the second node 1168 of thesecond planetary gear set 116 to the third node 114C of the firstplanetary gear set 114 and input shaft or member 112. A second clutch128 selectively connects the third node 118C of the third planetary gearset 118 to the second node 120B of the fourth planetary gear set 120. Afirst brake 130 selectively connects the second node 116B of the secondplanetary gear set 116 to the ground, stationary member, or transmissionhousing 150. A second brake 132 selectively connects the third node 118Cof the third planetary gear set 118 to the ground, stationary member, ortransmission housing 150. A third brake 134 selectively connects thethird node 120C of the fourth planetary gear set 120 to the ground,stationary member, or transmission housing 150.

Referring now to FIG. 5, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 100 according to thepresent invention. In FIG. 5, the numbering from the lever diagram ofFIG. 4 is carried over. The clutches, brakes and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, planetary gear set 114 is a planetary gear set thatincludes sun gear member 114C, planet gear carrier member 114B and ringgear member 114A. Sun gear member 114C is connected for common rotationwith input shaft or member 112. The planet gear carrier member 114Brotatably supports a set of planet gears 114D (only one shown) and isconnected for common rotation with a first interconnecting shaft ormember 142 and a second interconnecting shaft or member 144. Planetgears 114D are configured to each intermesh with both sun gear member114C and ring gear member 114A. Ring gear member 114A is connected forcommon rotation with a third interconnecting shaft or member 146.

The input shaft or member 112 is continuously connected to an engine(not shown) and to a turbine of a torque converter (not shown). Theoutput shaft or member 122 is continuously connected with the finaldrive unit or transfer case (not shown).

Planetary gear set 116 is a planetary gear set that includes sun gearmember 116A, planet carrier member 116B that rotatably supports a set ofplanet gears 116D and ring gear member 116C. Sun gear member 116A isconnected for common rotation with third interconnecting shaft or member146. Planet carrier member 116B is connected for common rotation with afourth interconnecting shaft or member 148. Planet gears 116D areconfigured to each intermesh with both sun gear member 116A and ringgear member 116C. Ring gear member 116C is connected for common rotationwith first interconnecting shaft or member 142.

Planetary gear set 118 is a planetary gear set that includes a sun gearmember 118C, a ring gear member 1188 and a planet carrier member 118Athat rotatably supports a first set of planet gears 118D (only oneshown) and a second set of planet gears 118E (only one shown). Sun gearmember 118C is connected for common rotation with a fifthinterconnecting shaft or member 152. Ring gear member 118B is connectedfor common rotation with second interconnecting shaft or member 144.Planet carrier member 118A is connected for common rotation with a sixthinterconnecting shaft or member 154 and output shaft or member 122.Planet gears 118D are configured to each intermesh with both sun gearmember 118C and second set of planet gears 118E. Second set of planetgears 118E are each configured to intermesh with both ring gear member1188 and first set of planet gears 118D.

Planetary gear set 120 is a planetary gear set that includes sun gearmember 120C, ring gear member 120A and planet carrier member 120B thatrotatably supports a set of planet gears 120D (only one shown). Sun gearmember 120C is connected for common rotation with a seventhinterconnecting shaft or member 156. Ring gear member 120A is connectedfor common rotation with sixth interconnecting shaft or member 154.Planet carrier member 120B is connected for common rotation with thirdinterconnecting shaft or member 146 and an eighth interconnecting shaftor member 158. Planet gears 120D are configured to intermesh with bothsun gear member 120C and ring gear member 120A.

The torque-transmitting devices or clutches 126, 128 and brakes 130, 132and 134 allow for selective interconnection of the shafts orinterconnecting members, members of the planetary gear sets and thehousing. For example, first clutch 126 is selectively engageable toconnect input shaft or member 112 and sun gear member 114C to fourthinterconnecting shaft or member 148. Second clutch 128 is selectivelyengageable to connect fifth interconnecting shaft or member 152 toeighth interconnecting shaft or member 158. First brake 130 isselectively engageable to connect fourth interconnecting shaft or member148 to ground, stationary member, or transmission housing 150 torestrict rotation of shaft or member 148 relative to housing 150. Secondbrake 132 is selectively engageable to connect fifth interconnectingshaft or member 152 to ground, stationary member, or transmissionhousing 150 to restrict rotation of shaft or member 152 relative tohousing 150. Third brake 134 is selectively engageable to connectseventh interconnecting shaft or member 156 to ground, stationarymember, or transmission housing 150 to restrict rotation of shaft ormember 156 relative to housing 150.

Referring now to FIGS. 5 and 6, the operation of the embodiment of theeight speed transmission 100 will be described. It will be appreciatedthat the transmission 100 is capable of transmitting torque from theinput shaft or member 112 to the output shaft or member 122 in at leasteight forward speeds or torque ratios and at least one reverse speed ortorque ratio. Each forward and reverse speed or torque ratio is attainedby engagement of one or more of the torque-transmitting devices (i.e.first clutch 126, second clutch 128, first brake 130, second brake 132and third brake 134), as will be explained below. FIG. 6 is a truthtable presenting the various combinations of torque-transmitting devicesthat are activated or engaged to achieve the various gear states. Actualnumerical gear ratios of the various gear states are also presentedalthough it should be appreciated that these numerical values areexemplary only and that they may be adjusted over significant ranges toaccommodate various applications and operational criteria of thetransmission 100. An example of the gear ratios that may be obtainedusing the embodiments of the present invention are also shown in FIG. 6.Of course, other gear ratios are achievable depending on the geardiameter, gear teeth count and gear configuration selected.

To establish reverse gear, first brake 130 and third brake 134 areengaged or activated. First brake 130 connects fourth interconnectingshaft or member 148 to ground, stationary member, or transmissionhousing 150 to restrict rotation of shaft or member 148 relative tohousing 150. Third brake 134 connects seventh interconnecting shaft ormember 156 to ground, stationary member, or transmission housing 150 torestrict rotation of shaft or member 156 relative to housing 150.Likewise, the eight forward ratios are achieved through differentcombinations of clutch and brake engagement, as shown in FIG. 6.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 100 assumes, first of all,that all clutches and brakes not specifically referenced in a given gearstate are inactive or disengaged and, second of all, that during gearshifts, i.e., changes of gear state, between at least adjacent gearstates, a clutch or brake engaged or activated in both gear states willremain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members; a first interconnecting member continuouslyinterconnecting the third member of the first planetary gear set withthe third member of the second planetary gear set and the first memberof the fourth planetary gear set; a first torque transmitting deviceselectively engageable to interconnect the first member of the secondplanetary gear set with at least one of the second member of the firstplanetary gear set and the input member; a second torque transmittingdevice selectively engageable to interconnect at least one of the thirdmember of the second planetary gear set, the third member of the firstplanetary gear set, and the first member of the fourth planetary gearset with the second member of the third planetary gear set; a thirdtorque transmitting device selectively engageable to interconnect thefirst member of the second planetary gear set with a stationary member;a fourth torque transmitting device selectively engageable tointerconnect the second member of the third planetary gear set with thestationary member; and a fifth torque transmitting device selectivelyengageable to interconnect the third member of the fourth planetary gearset with the stationary member, and wherein the torque transmittingdevices are selectively engageable in combinations of at least two toestablish at least eight forward speed ratios and at least one reversespeed ratio between the input member and the output member.
 2. Thetransmission of claim 1 further comprising a second interconnectingmember continuously interconnecting the first member of the firstplanetary gear set with the second member of the second planetary gearset and the first member of the third planetary gear set.
 3. Thetransmission of claim 1 further comprising a third interconnectingmember continuously interconnecting the third member of the thirdplanetary gear set with the second member of the fourth planetary gearset.
 4. The transmission of claim 1 wherein the second member of thefirst planetary gear set, the third member of the second planetary gearset, the second member of the third planetary gear set, and the thirdmember of the fourth planetary gear set are sun gears, the first memberof the first planetary gear set, the first member of the secondplanetary gear set, the third member of the third planetary gear set,and the first member of the fourth planetary gear set are carriermembers, and the third member of the first planetary gear set, thesecond member of the second planetary gear set, the first member of thethird planetary gear set, and the second member of the fourth planetarygear set are ring gears.
 5. The transmission of claim 1 wherein theinput member is continuously interconnected with the second member ofthe first planetary gear set and the output member is continuouslyinterconnected with at least one of the third member of the thirdplanetary gear set and the second member of the fourth planetary gearset.
 6. A transmission comprising: an input member; an output member;first, second, third and fourth planetary gear sets each having first,second and third members, wherein the input member is continuouslyinterconnected with the second member of the first planetary gear setand the output member is continuously interconnected with the thirdmember of the third planetary gear set and the second member of thefourth planetary gear set; a first interconnecting member continuouslyinterconnecting the first member of the first planetary gear set withthe second member of the second planetary gear set and the first memberof the third planetary gear set; a second interconnecting membercontinuously interconnecting the third member of the first planetarygear set with the third member of the second planetary gear set and thefirst member of the fourth planetary gear set; a first torquetransmitting device selectively engageable to interconnect the firstmember of the second planetary gear set with at least one of the secondmember of the first planetary gear set and the input member; a secondtorque transmitting device selectively engageable to interconnect atleast one of the third member of the second planetary gear set, thethird member of the first planetary gear set, and the first member ofthe fourth planetary gear set with the second member of the thirdplanetary gear set; a third torque transmitting device selectivelyengageable to interconnect the first member of the second planetary gearset with a stationary member; a fourth torque transmitting deviceselectively engageable to interconnect the second member of the thirdplanetary gear set with the stationary member; and a fifth torquetransmitting device selectively engageable to interconnect the thirdmember of the fourth planetary gear set with the stationary member, andwherein the torque transmitting devices are selectively engageable incombinations of at least two to establish at least eight forward speedratios and at least one reverse speed ratio between the input member andthe output member.
 7. The transmission of claim 6 wherein the secondmember of the first planetary gear set, the third member of the secondplanetary gear set, the second member of the third planetary gear set,and the third member of the fourth planetary gear set are sun gears, thefirst member of the first planetary gear set, the first member of thesecond planetary gear set, the third member of the third planetary gearset, and the first member of the fourth planetary gear set are carriermembers, and the third member of the first planetary gear set, thesecond member of the second planetary gear set, the first member of thethird planetary gear set, and the second member of the fourth planetarygear set are ring gears.
 8. A transmission comprising: an input member;an output member; first, second, third and fourth planetary gear setseach having a sun gear, a carrier member, and a ring gear, wherein theinput member is continuously interconnected with the sun gear of thefirst planetary gear set and the output member is continuouslyinterconnected with the carrier member of the third planetary gear setand the ring gear of the fourth planetary gear set; a firstinterconnecting member continuously interconnecting the carrier memberof the first planetary gear set with the ring gear of the secondplanetary gear set and the ring gear of the third planetary gear set; asecond interconnecting member continuously interconnecting the ring gearof the first planetary gear set with the sun gear of the secondplanetary gear set and the carrier member of the fourth planetary gearset; a first torque transmitting device selectively engageable tointerconnect the carrier member of the second planetary gear set with atleast one of the sun gear of the first planetary gear set and the inputmember; a second torque transmitting device selectively engageable tointerconnect at least one of the sun gear of the second planetary gearset, the ring gear of the first planetary gear set, and the carriermember of the fourth planetary gear set with the sun gear of the thirdplanetary gear set; a third torque transmitting device selectivelyengageable to interconnect the carrier member of the second planetarygear set with a stationary member; a fourth torque transmitting deviceselectively engageable to interconnect the sun gear of the thirdplanetary gear set with the stationary member; and a fifth torquetransmitting device selectively engageable to interconnect the sun gearof the fourth planetary gear set with the stationary member, and whereinthe torque transmitting devices are selectively engageable incombinations of at least two to establish at least eight forward speedratios and at least one reverse speed ratio between the input member andthe output member.